Catheter with omni-directional optical lesion evaluation

ABSTRACT

A catheter is adapted to ablate tissue and provide lesion qualitative information on a real time basis, having an ablation tip section with a generally omni-directional light diffusion chamber with one openings to allow light energy in the chamber to radiate the tissue and return to the chamber. The chamber is irrigated at a positive pressure differential to continuously flush the opening with fluid. The light energy returning to the chamber from the tissue conveys a tissue parameter, including without limitation, lesion formation, depth of penetration of lesion, cross-sectional area of lesion, formation of char during ablation, recognition of char during ablation, recognition of char from non-charred tissue, formation of coagulum around the ablation site, differentiation of coagulated from non-coagulated blood, differentiation of ablated from healthy tissue, tissue proximity, and recognition of steam formation in the tissue for prevention of steam pop.

FIELD OF INVENTION

The present invention relates to ablation catheters, and in particularto ablation catheters with lesion monitoring.

BACKGROUND

For certain types of minimally invasive medical procedures, real timeinformation regarding the condition of the treatment site within thebody is unavailable. This lack of information inhibits the clinicianwhen employing catheter to perform a procedure. An example of suchprocedures is tumor and disease treatment in the liver and prostate. Yetanother example of such a procedure is surgical ablation used to treatatrial fibrillation. This condition in the heart causes abnormalelectrical signals, known as cardiac arrhythmias, to be generated in theendocardial tissue resulting in irregular beating of the heart.

The most frequent cause of cardiac arrhythmias is an abnormal routing ofelectricity through the cardiac tissue. In general, most arrhythmias aretreated by ablating suspected centers of this electrical misfiring,thereby causing these centers to become inactive. Successful treatment,then, depends on the location of the ablation within the heart as wellas the lesion itself. For example, when treating atrial fibrillation, anablation catheter is maneuvered into the right or left atrium where itis used to create ablation lesions in the heart. These lesions areintended to stop the irregular beating of the heart by creatingnon-conductive barriers between regions of the atria that halt passagethrough the heart of the abnormal electrical activity.

The lesion should be created such that electrical conductivity is haltedin the localized region (transmurality), but care should be taken toprevent ablating adjacent tissues. Furthermore, the ablation process canalso cause undesirable charring of the tissue and localized coagulation,and can evaporate water in the blood and tissue leading to steam pops.

Currently, lesions are evaluated following the ablation procedure, bypositioning a mapping catheter in the heart where it is used to measurethe electrical activity within the atria. This permits the physician toevaluate the newly formed lesions and determine whether they willfunction to halt conductivity. It if is determined that the lesions werenot adequately formed, then additional lesions can be created to furtherform a line of block against passage of abnormal currents. Clearly, postablation evaluation is undesirable since correction requires additionalmedical procedures. Thus, it would be more desirable to evaluate thelesion as it is being formed in the tissue.

A known method for evaluating lesions as they are formed is to measureelectrical impedance. Biochemical differences between ablated and normaltissue can result in changes in electrical impedance between the tissuetypes. Although impedance is routinely monitored duringelectrophysiologic therapy, it is not directly related to lesionformation. Measuring impedance merely provides data as to the locationof the tissue lesion but does not give qualitative data to evaluate theeffectiveness of the lesion.

Another approach is to measure the electrical conductance between twopoints of tissue. This process, known as lesion pacing, can alsodetermine the effectiveness of lesion therapy. This technique, however,measures only the success or lack thereof from each lesion, and yieldsno real-time information about the lesion formation.

Thus, there is a need for a catheter capable of measuring lesionformation in real-time, as well as detecting the formation of charredtissue and coagulated blood around the ablation catheter. Because acatheter may assume various orientation angles at the ablation site,there is a further need for a catheter that is capable of such measuringand detecting whether the catheter is parallel, perpendicular or at anangle to the tissue. Moreover, where such measuring and detecting areaccomplished through optical spectroscopy, there is a also a need for acatheter that can minimize obstruction of optical pathways between thecatheter and the tissue undergoing ablation.

SUMMARY OF THE INVENTION

The present invention is directed to a catheter that is adapted forablation and provides optically-based lesion quantitative information ona real time basis. The catheter includes a catheter body and a tipsection configured for ablating tissue. In accordance with theinvention, the tip section has a light diffusion chamber with openingsthrough which light energy in the chamber can radiate and return fromthe tissue at a plurality of angles relative to the catheter.Additionally, the chamber may be irrigated with fluid, for example,saline, at a positive pressure differential to continuously flush theopenings with fluid. The light energy returning to the chamber from thetissue conveys tissue parameters that can be evaluated using opticalspectroscopy. These parameters include, without limitation, lesionformation, depth of penetration of lesion, and cross-sectional area oflesion, formation of char during ablation, recognition of char duringablation, recognition of char from non-charred tissue, formation ofcoagulum around the ablation site, differentiation of coagulated fromnon-coagulated blood, differentiation of ablated from healthy tissue,tissue proximity, evaluation of tissue health, status, and diseasestate, and recognition of steam formation in the tissue for preventionof steam pop.

In one embodiment of the catheter, light energy for radiating tissue isdelivered to the light diffusion chamber of tip section by a firstoptical waveguide, for example, a fiber optic cable. Most if not all ofthe light energy is specularly or diffusely scattered in the chamberbefore exiting through the openings to radiate the tissue. Uponreflection by the tissue back into the chamber through the openings,most if not all of the light energy is again scattered by the chamberbefore it is collected by a second optical guide, for example, anotherfiber optic cable, for optical processing and evaluation by a detectioncomponent and a quantification apparatus. In an alternative embodiment,a single optical waveguide may be used for delivering the radiationlight energy to the chamber and collecting the light energy from thechamber for optical processing and evaluation system.

Advantageously, the catheter is functional for ablation and lesionevaluation for nearly all angles of orientation with the tissue. To thatend, the light diffusion chamber is defined by portions of the tipelectrode that are oriented at different angles relative to thelongitudinal axis of the tip electrode. In one embodiment, there are afirst portion that is generally perpendicular to the longitudinal axis,a second portion that is angled between about zero and 90 degrees to thelongitudinal axis, preferably between about 20 to 70 degrees, and morepreferably about 45 degrees, and a third portion that is generallyparallel to the longitudinal axis. At least one opening is configured ineach portion of the tip electrode so that light energy in the reflectionchamber can radiate the tissue and re-enter the reflection chamber fornearly all angles of orientation relative to the catheter tip section.Accordingly, these portions of the tip electrode and the openingsprovided therein render the reflection chamber a generallyomni-directional radiator and collector of light energy for ablationtissue optical spectroscopy.

With adaptations for light energy to exit and enter the chamber fornearly all angles of orientation, the catheter can ablate and facilitatelesion evaluation in real time whether the catheter is lying on thetissue, standing on its distal end or at an angle with the tissue. In adetailed embodiment, there are a plurality of openings in the second andthird portions. In a more detailed embodiment, there are one opening inthe first portion, three openings in the second portion and six openingsin the third portion.

The catheter may be uni or bidirectionally with a deflectableintermediate section between the catheter body and the tip section. Thetip section may include a tip electrode having a shell and a plug whoseassembly defines the chamber within the tip electrode, wherein the tipelectrode is constructed of a thermally and electrically conductivematerial. The catheter may carry a temperature sensor and/or anelectromagnetic location sensor carried at or near the tip section forproducing electrical signals indicative of a location of theelectromagnetic location sensor.

The present catheter and optical system are designed to use light inconjunction with irrigation and the technology of RF ablation.Advantageously, the light used to monitor and assess the lesion isgenerally not affected by the portion of the electromagnetic radiationused for ablation. Moreover, the bandwidth used for monitoring andassessing also transmits through blood with minimal attenuations. Thefiber optics are used and disposed in the catheter in a manner thatavoids contact with tissue, which can increase the operative lifetime ofthe catheter and minimize damages caused by abrasion to the fiberoptics. Furthermore, the fiber optics are disposed in a tip section withminimal bent or strain but increased angular coverage, which canminimize fiber optics breakage during assembly and use, as well asreduce nonlinear optical effects caused by orientation of the fiberoptics. In addition, the use of fiber optics to emit and receive lightis a generally temperature neutral process that adds little if anymeasurable heat to surrounding blood or tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a side cross-sectional view of an embodiment of the catheterof the invention.

FIG. 2A is a side cross-sectional view of an embodiment of a catheterbody according to the invention, including the junction between thecatheter body and intermediate section taken along a first diameter.

FIG. 2B is a side cross-sectional view of an embodiment of a catheterbody according to the invention, including the junction between thecatheter body and intermediate section taken along a second diametergenerally perpendicular to the first diameter of FIG. 2A.

FIG. 3A is a side cross-sectional view of an embodiment of a catheterbody according to the invention, including the junction between theintermediate section and tip section taken along a first diameter.

FIG. 3B is a side cross-sectional view of an embodiment of a catheterbody according to the invention, including the junction between theintermediate section and tip section taken along a second diametergenerally perpendicular to the first diameter of FIG. 3A.

FIG. 3C is a longitudinal cross-sectional view of an embodiment of anintermediate section of FIGS. 3A and 3B, taken along line 3C-3C.

FIG. 4A is a side cross-sectional view of a catheter tip section showingan embodiment having an irrigated omni-directional light diffusionchamber taken along a first diameter.

FIG. 4B is a side cross-sectional view of an embodiment of a cathetertip section taken along a second diameter

FIG. 4C is a longitudinal cross-sectional view of an embodiment of acatheter tip section of FIGS. 4A and 4B, taken along line 4C-4C.

FIG. 5 is an end view of the distal end of an embodiment of a tipelectrode showing angled portions and optical openings.

FIG. 6A is a side view of an embodiment of a tip section whoselongitudinal axis is generally perpendicular to tissue surface.

FIG. 6B is a side view of an embodiment of a tip section whoselongitudinal axis is generally at an angle between zero and 90 to tissuesurface.

FIG. 6C is a side view of an embodiment of a tip section whoselongitudinal axis is generally parallel to tissue surface.

FIG. 7 is a side cross-section view of an embodiment of a shell of a tipelectrode showing angled portions and openings.

FIG. 8 is a schematic drawing showing components of an embodiment of anoptical processing system for use with the catheter of the presentinvention.

FIG. 9 is a schematic drawing showing components of an alternativeembodiment of an optical processing system for use with the catheter ofthe present invention.

FIG. 10. is a side view of an alternative embodiment of a tip section.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 1-7, catheter 10 comprises an elongated catheter body12 having proximal and distal ends, a potentially deflectable (uni- orbi-directionally) intermediate section 14 at the distal end of thecatheter body 12, a tip section 36 at the distal end of the intermediatesection, and a control handle 16 at the proximal end of the catheterbody 12.

With reference to FIGS. 1, 2A and 2B, the catheter body 12 comprises anelongated tubular construction having a single, axial or central lumen18. The catheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 can be of anysuitable construction and made of any suitable material. A constructioncomprises an outer wall 22 made of an extruded plastic. The outer wall22 may comprise an imbedded braided mesh of stainless steel or the liketo increase torsional stiffness of the catheter body 12 so that, whenthe control handle 16 is rotated, the catheter body 12, the intermediatesection 14 and the tip section 36 of the catheter 10 will rotate in acorresponding manner.

Extending through the single lumen 18 of the catheter body 12 arecomponents, for example, lead wire and thermocouple wires protected by asheath, fiber optic cables, a first irrigation tube segment, compressioncoils through which puller wires extend, and an electromagnetic sensorcable. A single lumen catheter body can be preferred over a multi-lumenbody because it has been found that the single lumen body permits bettertip control when rotating the catheter. The single lumen permits thevarious components such as the lead wires, infusion tube, and the pullerwire surrounded by the compression coil to float freely within thecatheter body. If such wires, tube and cables were restricted withinmultiple lumens, they tend to build up energy when the handle isrotated, resulting in the catheter body having a tendency to rotate backif, for example, the handle is released, or if bent around a curve, toflip over, either of which are undesirable performance characteristics.

The outer diameter of the catheter body 12 is not critical, but ispreferably no more than about 8 french, more preferably 7 french.Likewise the thickness of the outer wall 22 is not critical, but is thinenough so that the central lumen 18 can accommodate the aforementionedcomponents. The inner surface of the outer wall 22 may be lined with astiffening tube 20, which can be made of any suitable material, such aspolyimide or nylon. The stiffening tube 20, along with the braided outerwall 22, provides improved torsional stability while at the same timeminimizing the wall thickness of the catheter, thus maximizing thediameter of the central lumen 18. The outer diameter of the stiffeningtube 20 is about the same as or slightly smaller than the inner diameterof the outer wall 22. Polyimide tubing may be preferred for thestiffening tube 20 because it may be very thin walled while stillproviding very good stiffness. This maximizes the diameter of thecentral lumen 18 without sacrificing strength and stiffness.

Referring also to FIGS. 3A, 3B and 3C, the intermediate section 14comprises a shorter section of tubing 19 having multiple lumens. Thetubing 19 is made of a suitable non-toxic material that is preferablymore flexible than the catheter body 12. A suitable material for thetubing 19 is non-braided polyurethane. The outer diameter of theintermediate section 14, like that of the catheter body 12, ispreferably no greater than about 8 french, more preferably 7 french. Thesize and number of the lumens is not critical. In an embodiment, theintermediate section 14 has an outer diameter of about 7 french (0.092inch). The tubing has a first off-axis lumen 30 and a second off-axislumen 32 that are generally about the same size, each having a diameterof from about 0.020 inch to about 0.024 inch, preferably 0.022 inch,along with a third off-axis lumen 34 and a fourth off-axis lumen 35,each having a slightly larger diameter of from about 0.032 inch to about0.038 inch, preferably 0.036 inch.

Referring to FIGS. 2A and 2B, a means for attaching the catheter body 12to the intermediate section 14 comprises an outer circumferential notch24 configured in the proximal end of the tubing 19 that receives theinner surface of the outer wall 22 of the catheter body 12. Theintermediate section 14 and catheter body 12 are attached by glue or thelike. Before the intermediate section 14 and catheter body 12 areattached, the stiffening tube 20 is inserted into the catheter body 12.The distal end of the stiffening tube 20 is fixedly attached near thedistal end of the catheter body 12 by forming a glue joint 23 withpolyurethane glue or the like. Preferably a small distance, e.g., about3 mm, is provided between the distal end of the catheter body 12 and thedistal end of the stiffening tube 20 to permit room for the catheterbody 12 to receive the notch 24 of the intermediate section 14. If nocompression coil is used, a force is applied to the proximal end of thestiffening tube 20, and, while the stiffening tube 20 is undercompression, a first glue joint (not shown) is made between thestiffening tube 20 and the outer wall 22 by a fast drying glue, e.g.cyanoacrylate. Thereafter a second glue joint 26 is formed between theproximal ends of the stiffening tube 20 and outer wall 22 using a slowerdrying but stronger glue, e.g., polyurethane.

If desired, a spacer can be located within the catheter body between thedistal end of the stiffening tube and the proximal end of the tipsection. The spacer provides a transition in flexibility at the junctionof the catheter body and intermediate section, which allows thisjunction to bend smoothly without folding or kinking. A catheter havingsuch a spacer is described in U.S. patent application Ser. No.08/924,616, entitled “Steerable Direct Myocardial RevascularizationCatheter”, the entire disclosure of which is incorporated herein byreference.

As illustrated in FIGS. 4A-4C, extending from the distal end of theintermediate section 14 is the tip section 36 that includes a tipelectrode 37 and a plastic housing 21 extending between the tubing 19and the tip electrode 37. Preferably the tip electrode 37 has a diameterabout the same as the outer diameter of the tubing 19 of theintermediate section 14. The plastic housing 21 is preferably made ofpolyetheretherketone (PEEK) and may be about 1 cm long. Its proximal endcomprises an outer circumferential notch 27 (FIGS. 3A and 3B) thatreceives the inner surface of the tubing 19 of the intermediate section14. The intermediate section 14 and the plastic housing 21 are attachedby glue or the like.

As shown in the embodiment of FIGS. 4A and 4B, the tip electrode 37 hasa generally hollow distal portion and is of a two-piece construction. Inparticular, the tip electrode comprises a shell 38 of generally uniformthickness and a press-fit plug 39 positioned at or near the proximal endof the shell. The shell and the plug are formed from any suitablematerial that is both thermally and electrically conductive which allowsfor radio frequency ablation using an RF generator. Such suitablematerials include, without limitation, platinum, gold alloy, orpalladium alloy. A suitable tip electrode and method for manufacturingsame are disclosed in U.S. application Ser. No. 11/058,434, filed Feb.14, 2005, the entire disclosure of which is hereby incorporated byreference.

A tip electrode may have an effective length, i.e., from its distal endto the distal end of the housing 21, between about 3.5 mm to about 7.5mm, and an actual length, i.e., from its distal end to its proximal end,between about 4.0 mm to about 8. mm. As shown in FIGS. 4A and 4B, thetip electrode 37 is attached to the plastic housing 21 with glue at edge55 which is located at about a midpoint between the distal and proximalends of the plug 39. The wires, cables and tube that extend into theplug 39 help to keep the tip electrode in place on the tip section 36.

The tip electrode 37 is energized for RF ablation by a lead wire 40 thatextends through the third lumen 34 of intermediate section 14, thecentral lumen 18 of the catheter body 12, and the control handle 16, andterminates at its proximal end in an input jack (not shown) that may beplugged into an appropriate monitor (not shown). The portion of the leadwire 40 extending through the central lumen 18 of the catheter body 12,control handle 16 and distal end of the intermediate section 14 isenclosed within a protective sheath 52, which can be made of anysuitable material, preferably Teflon®. The protective sheath 52 isanchored at its distal end to the distal end of the intermediate section14 by gluing it in the lumen 34 with polyurethane glue or the like. Thelead wire 40 is attached to the tip electrode 37 by any conventionaltechnique. In the illustrated embodiment, connection of the lead wire 40to the tip electrode 37 is accomplished, for example, by welding thedistal end of the lead wire 40 into a first blind hole 31 (FIG. 4B) inthe plug 39 of the tip electrode 37.

A temperature sensing means is provided for the tip electrode 37 in thedisclosed embodiment. Any conventional temperature sensing means, e.g.,a thermocouple or thermistor, may be used. With reference to FIG. 4B, asuitable temperature sensing means for the tip electrode 37 comprises athermocouple formed by a wire pair. One wire of the wire pair is acopper wire 41, e.g., a number 40 copper wire. The other wire of thewire pair is a constantan wire 45, which gives support and strength tothe wire pair. The wires 41 and 45 of the wire pair are electricallyisolated from each other except at their distal ends where they contactand are twisted together, covered with a short piece of plastic tubing63, e.g., polyimide, and covered with epoxy. The plastic tubing 63 isthen attached in a second blind hole 33 of the tip electrode 37, byepoxy or the like. The wires 41 and 45 extend through the third lumen 34in the intermediate section 14. Within the catheter body 12 the wires 41and 45 extend through the central lumen 18 within the protective sheath52 along with the lead wires 40. The wires 41 and 45 then extend outthrough the control handle 16 and to a connector (not shown) connectableto a temperature monitor (not shown). Alternatively, the temperaturesensing means may be a thermistor. A suitable thermistor for use in thepresent invention is Model No. AB6N2-GC14KA143T/37C sold byThermometrics (New Jersey).

Referring to FIGS. 2A, 3B and 4B, a pair of puller wires 42A and 42Bextend through the catheter body 12, are anchored at their proximal endsto the control handle 16, and are anchored at their distal ends to thetip section 36. The puller wires are made of any suitable metal, such asstainless steel or Nitinol, and is preferably coated with Teflon® or thelike. The coating imparts lubricity to the puller wires. Each pullerwire preferably has a diameter ranging from about 0.006 to about 0.010inches.

A compression coil 56 is situated within the catheter body 12 insurrounding relation to each puller wire. The compression coils 56extend from the proximal end of the catheter body 12 to the proximal endof the intermediate section 14 (FIG. 2A). The compression coils are madeof any suitable metal, preferably stainless steel. Each compression coilis tightly wound on itself to provide flexibility, i.e., bending, but toresist compression. The inner diameter of the compression coil ispreferably slightly larger than the diameter of the puller wires 42. TheTeflon® coating on the puller wires allows them to slide freely withinthe compression coils. If desired, particularly if the lead wire 40 isnot enclosed by a protective sheath 52, the outer surface of thecompression coils can be covered by a flexible, non-conductive sheath,e.g., made of polyimide tubing, to prevent contact between thecompression coils and any other wires within the catheter body 12.

As shown in FIG. 2A, each compression coil 56 is anchored at itsproximal end to the proximal end of the stiffening tube 20 in thecatheter body 12 by glue joint 50 and at its distal end to theintermediate section 14 by glue joint 51. Both glue joints 50 and 51preferably comprise polyurethane glue or the like. The glue may beapplied by means of a syringe or the like through a hole made betweenthe outer surface of the catheter body 12 and the central lumen 18. Sucha hole may be formed, for example, by a needle or the like thatpunctures the outer wall 22 of the catheter body 12 and the stiffeningtube 20 which is heated sufficiently to form a permanent hole. The glueis then introduced through the hole to the outer surface of thecompression coil 56 and wicks around the outer circumference to form aglue joint about the entire circumference of the compression coil.

With reference to FIGS. 2A, 3B and 4B, the puller wire 42A extends intothe first lumen 30 of the intermediate section 14. The puller wire 42Ais anchored at its distal end to the tip electrode 37 within the thirdblind hole 73 in the plug 39. The puller wire 42B extends into thesecond lumen 32 of the intermediate section 14. The puller wire 42 isanchored at its distal end to the tip electrode 37 within the fourthblind hole 75 in the plug 39. The blind holes 73 and 75 are positionedin generally opposing positions along a diameter of the tip electrode 37and the holes are generally aligned with the lumens 30 and 32,respectively, of the intermediate section 14 to provide bi-directionaldeflection in the intermediate and tip sections of the catheter. Amethod for anchoring the puller wires 42 within the tip electrode 37 isby crimping metal tubing 46 to the distal end of the puller wires 42 andsoldering the metal tubing 46 inside the blind holes 73 and 75.Anchoring the puller wires 42 within the tip electrode 37 providesadditional support, reducing the likelihood that the tip electrode 37will fall off. Alternatively, the puller wires 42 can be attached to theside of the tubing 19 of the intermediate section 14. Within the firstand second lumens 30 and 32 of the intermediate section 14, the pullerwires 42 extend through a plastic, preferably Teflon®, sheath 81, whichprevents the puller wires 42 from cutting into the wall of theintermediate section 14 when the intermediate section is deflected.

Longitudinal movement of the puller wire 42 relative to the catheterbody 12, which results in deflection of the tip section 36, isaccomplished by suitable manipulation of the control handle 16. Suitablecontrol handles are described in U.S. Pat. No. 6,602,242, the entiredisclosure of which is hereby incorporated by reference.

In the illustrated embodiment of FIGS. 4A, 4B and 4C, the tip section 36carries an electromagnetic sensor 72. In particular, the electromagneticsensor may be carried in the plastic housing 21, with its distal endanchored in a blind hole 79 formed in the plug 39. The electromagneticsensor 72 is connected to an electromagnetic sensor cable 74, whichextends through the third lumen 34 of the tip section 36, through thecentral lumen 18 of the catheter body 12, and into the control handle16. The electromagnetic sensor cable 74 then extends out the proximalend of the control handle 16 within an umbilical cord 78 to a sensorcontrol module 75 that houses a circuit board (not shown).Alternatively, the circuit board can be housed within the control handle16, for example, as described in U.S. patent application Ser. No.08/924,616, entitled “Steerable Direct Myocardial RevascularizationCatheter”, the disclosure of which is incorporated herein by reference.The electromagnetic sensor cable 74 comprises multiple wires encasedwithin a plastic covered sheath. In the sensor control module 75, thewires of the electromagnetic sensor cable 74 are connected to thecircuit board. The circuit board amplifies the signal received from theelectromagnetic sensor 72 and transmits it to a computer in a formunderstandable by the computer by means of the sensor connector 77 atthe proximal end of the sensor control module 75, as shown in FIG. 1.Because the catheter can be designed for single use only, the circuitboard may contain an EPROM chip which shuts down the circuit boardapproximately 24 hours after the catheter has been used. This preventsthe catheter, or at least the electromagnetic sensor, from being usedtwice. Suitable electromagnetic sensors for use with the presentinvention are described, for example, in U.S. Pat. Nos. 5,558,091,5,443,489, 5,480,422, 5,546,951, 5,568,809, and 5,391,199 andInternational Publication No. WO 95/02995, the disclosures of which areincorporated herein by reference. An electromagnetic mapping sensor 72may have a length of from about 6 mm to about 7 mm and a diameter ofabout 1.3 mm.

In accordance with a feature of the present invention, the catheter 10is adapted to facilitate optically-based real-time assessment ofablation tissue characteristics, including without limitation, lesionformation, depth of penetration of the lesion, cross-sectional area ofthe lesion, formation of char during ablation, recognition of charduring ablation, differentiation of char from non-charred tissue,formation of coagulum around the ablation site, differentiation ofcoagulated from non-coagulated blood, differentiation of ablated fromhealthy tissue, tissue proximity, and recognition of steam formation inthe tissue for prevention of steam pop. These assessments areaccomplished by measuring the light intensity at one or more wavelengthsthat is recaptured at the catheter resulting from the light radiatedfrom the catheter tip onto ablated tissue.

As shown in FIGS. 2B, 3A and 4A, an optical waveguide, e.g., a fiberoptic cable 43E, is provided in the catheter to transport light energyto the tip section 36. In the disclosed embodiment, the fiber opticcable 43E is protectively housed in the catheter from the control handle16 to the tip section 36. The cable 43E functions as a lighttransmitting cable in the tip section by transmitting light energy tothe tip section 36 from an external and/or internal light source. It isunderstood by one of ordinary skill in the art that optical waveguidesand fiber optic cables in general serve to transmit optical energy fromone end to the other, although these are not exclusive.

Light from the fiber optic cable 43E enters a light reflection chamber44 provided in the tip section 36 as shown in FIGS. 4A and 4B. In thedisclosed embodiment, the shell 38 and the plug 39 of the tip electrode37 are configured such that when assembled the light reflection chamber44 is provided at the distal end of the tip electrode 37. An interiorsurface 47 of the chamber is defined by an interior surface of the shell38 and a distal end of the plug 39, each of whose surfaces has beenpolished or otherwise prepared to specularly or diffusely scatterincidental light with minimum attenuation. The polished interior surfaceof the chamber serves to specularly scatter light throughout thechamber. Such specular scattering advantageously avoids “hot spots” inthe tip electrode 37 and creates generally equal optical intensity (oroptical flux defined in units of power per unit area) at every locationin the chamber and hence generally uniform optical intensity throughoutthe chamber. With reference to FIGS. 6A-6C, the specularly scatteredlight in the chamber radiates tissue 91 at the treatment site by passingthrough openings 80 configured in the shell 38 of the tip electrode 37.

As lesion 92 forms in the tissue 91 from ablation carried out by thecatheter 10 (or by another catheter), its characteristics are altered asunderstood by one of ordinary skill in the art. In particular, as thelesion is radiated, the radiation is scattered and/or reflected backtoward the tip section 36, where such light having interacted orotherwise having been affected by the lesion bears qualitative andquantitative information about the lesion 92 as it returns to thechamber through the openings 80.

Upon return to the reflection chamber 44, most if not all of the lightis again specularly scattered. With incidence on a receiving opticalreceiver, for example, a fiber optic cable 43R, provided in the chamber44, the light bearing the qualitative and quantitative information istransmitted to an optical processing system as described below infurther detail.

As shown in FIGS. 2B, 3A and 4A, the cables 43E and 43R are protectivelyhoused along the length of the catheter. They extend through the tubing18 of the catheter body 12, through the third lumen 34 of theintermediate section 14 and through passages 53 formed in the plug 39 ofthe tip electrode 37, with their distal ends anchored at or near thedistal end of the plug 39. The passages 53 are generally aligned withthe third lumen 34 of the intermediate section 14 to minimize stress onthe cables 43E and 43R in their transition between the intermediatesection 14 and the tip section 36.

The polished interior surface 47 of the chamber effectively scatters thelight from the cable 43E throughout the chamber 44, and enables thecollection of lesion optical data by the cable 43R despite the relativelocalized, stationary and off-axis dispositions of the distal ends ofthese cables. That is, such radiation and collection by the fiber opticcables are possible regardless of their positions in the chamber becauseof the isotropic scattering provided by the polished interior surface.This feature permits the tip section to be designed, manufactured orassembled with greater flexibility and adaptability. To furtherencourage isotropic scattering in the chamber, the shell 38 and the plug39 may be configured to avoid linear alignment between the distal endsof the cables 43 and the openings 80.

In accordance with a feature of the present invention, the tip section36 serves as a generally omni-directional optical radiator andcollector. In the disclosed embodiment, the shell 38 of the tipelectrode 37 is configured with portions 100 that provide differentangles of orientation relative to a longitudinal axis 102 of the tipelectrode. Accordingly, the tip section accomplishes effective radiationand collection of lesion optical data for nearly any angle oforientation between the catheter and the tissue of interest. Withreference to FIG. 7, the shell 38 of the tip electrode 37 is configuredwith (i) a first or distal portion 100 a whose surface is generallyperpendicular to the axis 102, (ii) a second or radial portion 100 bwhose surface is at an angle θ relative to the axis, where the angle θranges between about zero and 90 degrees, preferably between about 20and 70 degrees, and more preferably about 45 degrees, and (iii) a thirdor circumferential portion 100 c whose surface is generally parallel tothe axis. In the illustrated embodiment, the shell 38 is configured witha hollow dome design having a generally spherical, parabolic, or atleast rounded convex distal portion to provide the sections 100 and yetbe of an atraumatic design. With at least one if not more openings 80configured in each of sections 100, light can exit and enter the chamber44 from many different angles and directions.

With reference to the illustrated embodiment of FIG. 5, the firstportion 100 a has a single opening 80 that is located on or near thedistal most location of the electrode on the longitudinal axis 102 (orapex of the tip electrode), the second portion 100 b has three openings80 that are generally equi-angular from each other at about 120 degreesin circumference and at generally equi-distance from the apex, and thethird portion 100 c has six openings 80 that are generally equi-angularfrom each other at about 60 degrees in circumference and at generallyequi-distance from the apex. Thus, in the illustrated embodiment, atotal of ten openings are provided in the tip electrode 37. Moreover, itmay be desirable that the openings of different sections are radiallyoffset from each other for optimal radiation and capture of optical dataas best shown in FIG. 5 (where no openings of adjacent sections 100 band 100 c are aligned on any one radial line R). It is understood by oneof ordinary skill in the art that the plurality and configuration of theportions 100 and the openings 80 may be varied as appropriate ordesired. The size and dimensions of each portion may also be varied asappropriate or desired, as well as the shape of the openings, which canbe round, ovular, square, polygonal, flat(slit), or any combination ofthese shapes.

Such variously angled portions 100 (and their corresponding openings 80)advantageously enable generally omni-directional emission and collectionof radiation between the catheter and tissue. In FIG. 6A, the angle oforientation of the tip section 36 (generally defined by the longitudinalaxis 102 of the tip electrode 37 to the surface of the lesion 92) isabout 90 degrees, such that radiation of the lesion and collection oflesion optical data can be accomplished primarily through light passingthrough opening 80 a in the first portion 100 a, with perhapscontribution from the light passing through openings 80 c in the secondportion 100 b. In FIG. 6B, the angle of orientation is about 30 degrees,such that radiation of the lesion 92 and collection of lesion opticaldata can be accomplished primarily through light passing throughopenings 80 c in the second portion 100 b, with perhaps contributionfrom light passing through opening 80 a in the distal portion 100 aand/or openings 80 b in the third portion 100 c. In FIG. 6C, the angleof orientation is about zero degrees, such that radiation of the lesion92 and collection of lesion optical data can be accomplished primarilythrough light passing through openings 80 b in the third portion 100 c,with perhaps contribution from light passing through openings 80 c ofthe second portion 100 b.

It is understood that the fiber optic cables 43E and 43R may be anysuitable optical wave guide wherein light introduced at one of the cableis guided to the other end of the cable with minimal loss. Each of thecables 43E and 43R may be a single fiber optic cable or fiber bundles.They may be single mode (also known as mono-mode or uni-mode),multi-mode (with step index or graded index) or plastic optical fiber(POF), depending on a variety of factors, including but not limited totransmission rate, bandwidth of transmission, spectral width oftransmission, distance of transmission, diameter of cable, cost, opticalsignal distortion tolerance and signal attenuation, etc.

To keep the openings 80 generally free from obstruction from blood orother bodily fluids and tissue encountered by the tip electrode 37, thetip electrode is irrigated with fluid, e.g., saline, that is fed intothe chamber 44 by an irrigation tube segment 48 that extends from thedistal end of the fourth lumen 35 of the intermediate section 14,through the plastic housing 21 and passage 95 in the plug 39. The distalend of the segment 48 is anchored in the passage 95 and the proximal endis anchored in the fourth lumen 35 by polyurethane glue or the like. Thepassage 95 is generally aligned with the fourth lumen 35 of theintermediate section 14. The segment 48, like the puller wires 42,provides additional support for the tip electrode. The irrigation tubesegment 48 is in communication with a proximal infusion tube segment 88that extends through the central lumen 18 of the catheter body 12 andterminates in the proximal end of the fourth lumen 35 of theintermediate section 14. The distal end of the proximal infusion tubesegment 88 is anchored in the fourth lumen 35 by polyurethane glue orthe like. The proximal end of the first infusion tube segment 88 extendsthrough the control handle 16 and terminates in a luer hub 90 (FIG. 1)or the like at a location proximal to the control handle. In practice,fluid may be injected by a pump (not shown) into the infusion tubesegment 88 through the luer hub 90, and flows through the segment 88,through the fourth lumen 35, through the infusion tube segment 48, intothe chamber 44 in the tip electrode 37, and out the openings 80. Theinfusion tube segments may be made of any suitable material, and ispreferably made of polyimide tubing. A suitable infusion tube segmenthas an outer diameter of from about 0.32 inch to about 0.036 inch and aninner diameter of from about 0.28 inch to about 0.032 inch.

In accordance with a feature of the present invention, the pumpmaintains the fluid at a positive pressure differential relative tooutside the chamber 44 so as to provide a constant unimpeded flow orseepage of fluid outwardly from the chamber 44 which continuouslyflushes the openings 80 and minimizes obstruction so light can freelypass through for the aforementioned radiation and collection purposes.In addition to the above, the irrigation adaptation of the catheter 10may serve other typical functions such as cooling the tip electrodeand/or the ablation site and increasing conduction for deeper and largerlesions.

With reference to FIG. 8, an optical processing system 110 for opticallyevaluating ablation tissue using the catheter 10 is illustrated. A lightsource 120 supplies a broadband (white; multiple wavelengths) lightand/or laser light (single wavelength) radiation to the tip section 36of the catheter 10 via the emitting cable 43E, and light bearing lesionqualitative information from the tip section is transmitted by thereceiving cable 43R to a detection component 130. The detectioncomponent may comprise, for example, a wavelength selective element 131that disperses the collected light into constituent wavelengths, and aquantification apparatus 140. The at least one wavelength selectiveelement 131 includes optics 132, as are known in the art, for example, asystem of lenses, mirrors and/or prisms, for receiving incident light 34and splitting it into desired components 136 that are transmitted intothe quantification apparatus 140.

The quantification apparatus 140 translates measured light intensitiesinto an electrical signal that can be processed with a computer 142 anddisplayed graphically to an operator of the catheter 10. Thequantification apparatus 140 may comprise a charged coupled device (CCD)for simultaneous detection and quantification of these lightintensities. Alternatively, a number of different light sensors,including photodiodes, photomultipliers or complementary metal oxidesemiconductor (CMOS) detectors may be used in place of the CCDconverter. Information is transmitted from the quantification device 140to the computer 142 where a graphical display or other information isgenerated regarding parameters of the lesion. A suitable system for usewith the catheter 10 is described in U.S. application Ser. No.11/281,179 entitled Apparatus for Real Time Evaluation of TisueAblation, and Ser. No. 11/281,853 entitled Method for Real TimeEvaluation of Tissue Ablation, the entire disclosures of which arehereby incorporated by reference.

In an alternative embodiment as illustrated in FIG. 9, the fiber opticcables 43E and 43R are replaced by a single fiber optic cable 143 suchthat light to and from the chamber 44 travel through the cable 143 inopposite directions. A beam splitter 150 or the like is provided tosplit the optical path such that light from the light source 120 travelsto the catheter through an optical waveguide, e.g., fiber optic 145,through the beamsplitter and through the cable 143, and light from thechamber 44 travels through the cable 143, the beamsplitter 150 andthrough an optical waveguide, e.g., fiber optic 148, to the detectioncomponent 130 and quantification apparatus 140.

In another alternative embodiment as illustrated in FIG. 10, a lens 155is positioned over the fiber optical cables 43E and 43C or optical cable143 to diffusely scatter the light emitted and collected by the cables,in addition to the polished interior surface of the chamber 44. In thisillustrated embodiment, the tip electrode 37 is attached to the plastichousing 21 by creating a circumferential notch 37 in the distal end ofthe housing 21, placing the proximal end of the tip electrode on thedistal end of the housing 21, and filling the notch 37 with glue. It isunderstood by one of ordinary skill in the art that the notch 37 may beformed in the proximal end of the tip electrode to accomplish attachmentto the housing 21 and that a variety different means and structures canbe used accomplish this attachment.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention.

Accordingly, the foregoing description should not be read as pertainingonly to the precise structures described and illustrated in theaccompanying drawings, but rather should be read consistent with and assupport to the following claims which are to have their fullest and fairscope.

What is claimed is:
 1. A catheter, comprising: a catheter body; a tipsection distal the catheter body adapted for radiofrequency ablation oftissue, the tip section comprising a distal end having a light diffusionchamber adapted to diffusively scatter light, the distal end of the tipsection comprising at least a first portion having a surface generallyperpendicular to a longitudinal axis of the tip section, a secondportion having a surface at an angle θ ranging from about 0 to about 90°relative to the longitudinal axis of the tip section, and a thirdportion having a generally circumferential surface that is generallyparallel to the longitudinal axis of the tip section; wherein the lightdiffusion chamber has at least three openings configured for passage oflight to and from the tissue at a plurality of angles, wherein each ofthe first, second and third portions of the tip section carries at leastone of the at least three openings and the at least one opening of thesecond portion is radially offset from the at least one opening of thethird portion, the catheter further comprising means for emitting lightthrough the openings to radiate the tissue, and means for collectinglight returning to the light diffusion chamber through the openings, thelight diffusion chamber comprising a polished interior wall configuredto scatter light in the light diffusion chamber.
 2. A catheter of claim1, further comprising irrigation means for irrigating the lightdiffusion chamber and flushing the openings with fluid.
 3. A catheter ofclaim 1, wherein the means for emitting light comprises at least a firstoptical waveguide to deliver light energy to the light diffusion chamberand wherein the means for collecting light comprises at least a secondoptical waveguide to receive light from the light diffusion chamber. 4.A catheter of claim 1, wherein the light diffusion chamber is formedwithin a tip electrode of the tip section.
 5. A catheter of claim 1,wherein the angle θ of the second portion is about 45 degrees.
 6. Acatheter of claim 1, wherein the first portion has one opening, thesecond portion has three openings, and the third portion has sixopenings.
 7. A catheter according to claim 6, further comprising meansfor deflecting the tip section.
 8. A catheter of claim 1, wherein thetip section includes a tip electrode having a shell and a plug, whereinthe polished wall of the light diffusion chamber comprises an interiorwall of the shell and a distal wall of the plug.
 9. A catheter adaptedto ablate tissue, comprising: a catheter body; a tip section distal thecatheter body adapted for radiofrequency ablation of tissue, the tipsection comprising a distal end having a light diffusion chamber with atleast three openings to allow light in the light diffusion chamber toradiate the tissue and return to the light diffusion chamber, the distalend of the tip section comprising at least a first portion having asurface generally perpendicular to a longitudinal axis of the tipelectrode, a second portion having a surface at an angle θ ranging fromabout 0 to about 90° relative to the longitudinal axis of the tipsection, and a third portion having a generally circumferential surfacethat is generally parallel to the longitudinal axis of the tip section,wherein each of the first, second and third portions of the tip sectioncarries at least one of the at least three openings of the lightdiffusion chamber and the at least one opening of the second portion isradially offset from the at least one opening of the third portion, thelight diffusion chamber comprising a polished interior wall configuredto scatter light in the light diffusion chamber; means for emittinglight through the openings to radiate the tissue; means for collectinglight returning to the light diffusion chamber through the openings; andirrigation means for irrigating the light diffusion chamber and flushingthe openings with fluid.
 10. A catheter of claim 9, wherein thedifferent first, second and third regions of the distal end of the tipsection provide different angles of incidence of the light on thetissue.
 11. A catheter of claim 9, wherein each of the different first,second and third portions of the distal end of the tip sectionaccommodate a different range of angles between the catheter tip sectionand the tissue.
 12. A catheter of claim 9, wherein the angle θ of thesecond portion ranges from about 20 to about 70 degrees.
 13. A catheterof claim 9, wherein the means for emitting light comprises a firstoptical guide to transmit light to the light diffusion chamber; andwherein the means for collecting light comprises a second optical guideto collect light in the light diffusion chamber.
 14. A catheter of claim9, further comprising a deflectable intermediate section between thecatheter body and the tip section.
 15. A catheter of claim 9, whereinthe tip section includes a tip electrode having a shell and a plug,wherein the polished surface of the light diffusion chamber comprises aninterior surface of the shell and a distal surface of the plug.
 16. Acatheter of claim 15, wherein the tip electrode is made of thermally andelectrically conductive material.
 17. A catheter of claim 9, wherein theirrigation means comprises a pump for maintaining the fluid in the lightdiffusion chamber at a positive pressure differential relative tooutside the tip section for generally continuous flushing of theopenings.
 18. A catheter of claim 9, wherein the catheter is adapted toprovide optical data of the tissue at angles between a longitudinal axisof the tip section and the tissue ranging between about zero and about90 degrees.
 19. A catheter of claim 9, wherein the means for emittinglight and the means for collecting light comprise a single optical guideextending through the catheter body and a proximal portion of the tipsection, the optical guide being configured for two-way transmission ofthe light.
 20. A catheter of claim 9, further comprising anelectromagnetic location sensor carried at or near the tip section forproducing electrical signals indicative of a location of theelectromagnetic location sensor.
 21. A catheter of claim 9, furthercomprising a temperature sensor.
 22. A catheter adapted to ablatetissue, comprising: a catheter body; a tip section distal the catheterbody adapted for radiofrequency ablation of tissue, the tip sectioncomprising a distal end having a tip electrode with a light diffusionchamber with at least three openings to allow light energy in the lightdiffusion chamber to radiate the tissue and return to the lightdiffusion chamber, the distal end of the tip section comprising at leasta first portion having a surface generally perpendicular to alongitudinal axis of the tip electrode, a second portion having asurface at an angle θ ranging from about 0 to about 90° relative to thelongitudinal axis of the tip section, and a third portion having agenerally circumferential surface that is generally parallel to thelongitudinal axis of the tip section, wherein each of the first, secondand third portions of the tip section carries at least one of the atleast three openings of the light diffusion chamber and the at least oneopening of the second portion is radially offset from the at least oneopening of the third portion, the light diffusion chamber comprising apolished interior wall configured to scatter light in the lightdiffusion chamber; means for emitting light through the openings toradiate the tissue; means for collecting light returning to the lightdiffusion chamber through the openings; and irrigation means forirrigating the light diffusion chamber and flushing the openings withfluid.
 23. A catheter of claim 22, wherein the angle of the secondportion is between about 20 and 70 degrees.
 24. A catheter of claim 22,wherein the angle θ of the second portion is about 45 degrees.